젖소 분뇨의 마이크로파-알칼리(NaOH) 전처리: 용해도 향상 및 이론적 메탄 생성량 예측

Microwave-Alkali (NaOH) Pretreatment of Dairy Manure: Enhancement of Solubilization and Theoretical Methane Yield Prediction

Abera Jabessa Fufa1, Wardhani Riuh1, 송용우2, 박성준2, 김동여2, 김수현1, 이종옥4, 신진호1, 이승훈4, 안희권3*

Abera Jabessa Fufa1, Riuh Wardhani1, Yongwoo Song2, Seongjun Park2, Dongyeo Kim2, Suhyun Kim1, Jongok Lee4, Jinho Shin1, Seunghoon Lee4, Heekwon Ahn3*

1충남대학교 낙농학과, 2충남대학교 축산환경학과, 3충남대학교 동물자원과학부, 4충남대학교 농업과학연구소

1 Dept. of Dairy Science, Chungnam National University, Daejeon, Korea

2Dept. of Livestock Environment Chungnam National University, Daejeon, Korea

3Division of Animal and Dairy Science, Chungnam National University, Daejeon, Korea

4Institute of Agricultural Science, Chungnam National University, Daejeon, Korea

*교신저자: 안희권*(hkahn@cnu.ac.kr)

This study evaluated the effect of combined microwave and sodium hydroxide (NaOH) pretreatment on the solubilization of fresh dairy manure and its implications for anaerobic digestion. Six treatment groups were analyzed: G01 (control), G02 (microwave only), G03 (3% NaOH), G04 (6% NaOH), G05 (3% NaOH+ microwave), and G06 (6% NaOH+microwave). Dairy manure was pretreated by microwave heating at 90°C for 5 minutes, followed by NaOH addition at 3% and 6% (w/w total solids) with a reaction time of 30 minutes. Pretreatment significantly enhanced organic matter solubilization, as evidenced by increased soluble chemical oxygen demand (SCOD) across all treated groups compared to the control (p<0.05). Notably, G04 and G06 exhibited the highest COD solubilization efficiencies of 24% and 25%, respectively (p<0.05 vs. control). In parallel, significant increases in total dissolved solids (TDS) and volatile dissolved solids (VDS) were observed in the NaOH and microwave-treated groups compared to the control, confirming improved release of soluble organic matter. G06 recorded the highest TDS (mean: 18,228 mg/L) and VDS (mean: 8,434 mg/L), indicating enhanced solubilization efficiency under combined 6% NaOH and microwave pretreatment (p<0.05). To estimate the impact on methane production potential, theoretical methane yields were calculated based on SCOD values using the stoichiometric conversion factor of 0.35 L CH₄/g COD. Theoretical methane yields normalized by volatile solids (VS) added were: G01 (110.16 ml CH₄/g VS), G02 (110.16ml CH₄/g VS), G03 (272.30 ml CH₄/g VS), G04 (455.26 ml CH₄/g VS), G05 (232.48 ml CH₄/g VS), and G06 (481.95 ml CH₄/g VS). There were statistically significant differences among treatment groups (p<0.05). The findings demonstrate that SCOD- and VDS-based methane yield estimation highlights the enhanced biodegradability potential of dairy manure following microwave–alkali pretreatment, particularly with 6% NaOH, and supports its applicability for improving anaerobic digestion efficiency.

*키워드(Keywords): Dairy manure, Microwave-alkali pretreatment, Solubilization, Anaerobic digestion, Theoretical methane yield

*사사(Acknowledgment): Livestock Environmental laboratory, Chungnam National University